When shooting families, I go big or go home. You need that long focal length to provide separation between your clients and the background.
I try to shoot 85mm or higher for beautiful, classic family portraits.

85mm 1.4 - 1/800 f2.2 ISO 320

85mm 1/1000 f2.2. ISO 320

85mm 1/800 f2.2. ISO 320

70-200mm, zoomed in to 200mm 1/320 f2.8 ISO500

70-200mm 1/500 f2.8 ISO500 - you can shoot wide open as long as all the subjects are on the same plain of focus.